The present invention relates to a dial or half-dial for single-cylinder circular hosiery knitting machines, particularly for producing tubular items closed at one longitudinal end.
It is known that some types of single-cylinder circular hosiery knitting machines, in order to perform particular types of knitting, are equipped with a dial which is arranged above the needle cylinder and coaxially thereto. The dial of these machines generally has a substantially disk-like body, on the upper face whereof there is a plurality of radial slots, each accommodating a hook which can be actuated along the corresponding radial slot in order to cooperate, thanks to its hooked end that protrudes from the dial body, with the needles in manufacturing the items.
A cover for closing the radial slots in an upward region and therefore retain the hooks inside the corresponding radial slots, is generally arranged above the dial body. Furthermore, the hook actuation cams are associated with the cover of the dial. Said cams form paths which can be engaged by the heels of the hooks, which protrude upwards from the radial slots, so as to produce the movement of the hooks, inside the corresponding radial slots of the dial body, towards or away from the axis of the dial in order to perform the various kinds of knitting.
The cover as an element for closing the radial slots in an upward region, in addition to significantly increasing the mass of the dial as a whole and considerably affecting production and assembly costs, causes problems during maintenance of the dial or hooks.
In these situations it is in fact often necessary to fully remove the dial from the machine and disassemble the cover in order to be able to access the hooks located in the radial slots of the dial body.
These problems are even greater in the case of single-cylinder circular hosiery knitting machines which can close a longitudinal end of the tubular knitted item during its production.
These machines are in fact generally provided with a half-dial which is located above the needle cylinder of the machine so as to overlap one half of the needle cylinder and can be turned over, substantially through an angle of 180.degree., about a diametrical axis of the needle cylinder in order to face one half of the needle cylinder or the other half of the needle cylinder. Inside the overturning half-dial there is a plurality of radial slots or twin radial slots, in each of which two or more hooks with mutually opposite hooked ends are arranged. The hooks of each slot or twin slot can be actuated individually in order to engage the loops formed by the needles of one half of the needle cylinder and to retain them inside the hooked ends during the overturning of the half-dial about the diametrical axis. After overturning, the hooks are actuated again so as to release the previously retained loops, which are engaged by the needles of the other half of the needle cylinder.
After transferring the loops formed by one half of the needle cylinder to the needles of the other half of the needle cylinder, one longitudinal end of the tubular item produced by the circular hosiery knitting machine is closed.
The hooks used in these machines are generally provided with a heel which protrudes upwards from the half-dial body and with a heel which protrudes downwards from the half-dial. Because of this, on the bottom of the radial slots there is an adapted slit for the passage of the heel which must protrude downwards from the half-dial.
Above the half-dial there are also cams which determine paths for said heels, so as to produce the coordinated movement of the hooks in a radial direction with respect to the axis of the needle cylinder in order to engage or release the loops of knitting.
When the half-dial is turned over about the diametrical axis, the hooks engage said cams by means of the heel which, in the non-overturned position, protruded downwards from the dial.
In these kinds of machine the cover on the half-dial, which is required in order to retain the hooks inside the corresponding radial slots of the half-dial, causes additional problems, since it significantly increases the mass of an element which must be overturned and increases the complexity of the production and assembly of the half-dial, and interventions on the hooks in case of maintenance are even more difficult indeed because it is necessary to disassemble the cover arranged on the half-dial.